Hydrotropically Prepared Starch Gels as Topical Drug Delivery A Rheological StudyAuthor(s): K. Purushotham Rao, Md. Najmuddin and B. Satyanath
Rheologic behaviour of hydrotropically prepared potato starch gels using sodium salicylate in presence and absence of two added polyols ; (propylene glycol and polyethylene glycol) each at 3% concentration was studied with the help of Brookfield Synchroelectirc RVT model digital viscometer with spindle No. SC428/13R. The apparent viscosity (cp) values were found to be 116780 and 3130; 100780 and 3620; 159780 and 3955 respectively for blank gel, gel with polyethylene glycol 6000 and gel with propylene glycol at low shear rate 0.14 sec-1 and high shear rate 28 sec-1 at room temperature . The results conclusively proved that all the three types of gels exhibited shear thinning tendency. Stress- Shear rate rheograms indicated that the gel systems are pseudoplastic and exhibited thixotropy. The data further indicated when plotted as Casson and Fitch plots. Both the methods of plotting were found to generate unambiguous intercepts for calculating yield values and were found to be 18975, 20140 and 20638 dynes/cm2 for blank gel, gel with polyethylne glycol 6000 and gel with propylene glycol, respectively form Casson plots. The added polyols were found to increase apparent viscosity of the prepared hydrotropically gelled potato starch and were found to be in order PG > PEG > Blank.